Biological Control of Fusarium Wilt Disease of Tomato Plants Using Seaweed Extracts.

The present research was conducted to evaluate the marine algal extracts effectiveness on tomato Fusarium wilt disease. The organic extracts of macroalgae exhibited antagonistic activity against Fusarium oxysporum. The highest antifungal activity obtained from the methanolic extract of Cystoseira myrica followed by methanol extract of Sargassum cinereum. GC-mass analysis of some seaweed extracts was used to identify the presence of main compounds as dimethylocta-1,6-dien-3-ol,1- methoxy-4-(2-propenyl), hexadecanoic acid, methyl ester, and octadecanoic acid, and methyl ester. The infection of tomato plants with F. oxysporum induced a significant decrease in shoot and root dry weights as well as the photosynthetic pigments. There was a marked increase in soluble contents of saccharides and protein for infected tomato plant shoots and roots. On the other hand, pathogenicity stress induced a significant decrease in total contents of saccharides and protein of tomato shoots and roots. The results indicated a significant increase in total free amino acid content and antioxidant enzymes (CAT, POD, and APX)activities of inoculated tomato shoots and roots. The plant fresh and dry weights increased significantly by increasing its pigments content as a result of marine algal extracts application. On the other hand, algal extracts pretreatment decreased soluble saccharides and protein contents of plants, whereas increased significantly amino acid content in shoots of the inoculated plants. The increase in the activity of antioxidant enzymes played an essential role in increasing plant resistance against F. oxysporum. Finally, the marine macroalgae could serve as a new bioagent source for biological control of soil fungi.